What is the concensus on when to use one of these tools adversed to the other? I find Subsonic very useful in terms of getting things done quickly, but on large projects it
Slightly off topic, but in a similar vein. Have you looked at Castle ActiveRecord it is written on top of NHibernate and removes the need to spend time creating XML mappings from code to the database. Like NHibernate you can structure your domain objects as you want and later generate a database schema from this structure.
Using ActiveWriter, a contributed tool, you can easily map from your database to domain objects.